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Zhihui She, Li-Fang Hung, Baskar Arumugam, Krista M Beach, Earl L Smith; Effects of reduced ambient lighting on refractive development in infant rhesus monkeys. Invest. Ophthalmol. Vis. Sci. 2019;60(9):3159.
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© ARVO (1962-2015); The Authors (2016-present)
While elevated ambient lighting has been shown to promote hyperopia and to reduce the degree of form-deprivation myopia (FDM) in several animal species, low ambient light-levels promote the development of myopia in young chicks. The purpose of this study was to determine the effects of reduced ambient lighting (“dim” light or DL) on normal emmetropization and the ametropias produced by altered visual experiences in infant primates.
Starting at 3 weeks of age, rhesus monkeys were randomly assigned to experimental groups reared with unrestricted vison (dim light normal vision, DL NV, n=5), monocular form-deprivation (DL FD, n=7), or imposed monocular hyperopic (DL -3D, n=8) or myopic defocus (DL +3D, n=6) and were housed under reduced ambient lighting (7 to 36 lux at cage-level) until 130 to 150 days of age. Refractive error (RE) and ocular dimensions were measured periodically. Control data were obtained from monkeys reared without visual restriction (normal light normal vision, NL NV, n=39) and monkeys subject to the same lens- and diffuser-rearing regimens (NL FD, NL -3D, NL +3D; n=16, 18, and 7, respectively), but housed under typical laboratory lighting (203 to 682 lux).
Although the interocular differences in RE were more variable in DL NV- than NL NV-monkeys, DL did not produce myopia (DL NV median ametropias: OD: +3.13D, OS: +3.56D, range +2.06 to +6.00 D). DL also did not enhance the myopic anisometropia produced by either form-deprivation or lens-induced hyperopic defocus (DL FD: -3.69D, NL FD: -4.88D, p=0.44; DL -3D: -0.44D, NL -3D: -2.44D, p=0.13). The absolute myopic errors in the treated eyes of the DL FD and DL -3D monkeys were similar to those observed in the NL FD and NL -3D monkeys. (DL FD: -4.13D, NL FD: -1.19D, p=0.54; DL -3D: +0.28D, NL -3D: +0.28D, p=0.54). However, DL reduced the likelihood that monkeys would compensate for myopic defocus. Whereas hyperopic anisometropia was observed in all 9 NL +3D monkeys, only 2 of the 6 DL +3D monkeys exhibited such compensation (DL +3D: -0.58±0.91D, NL +3D: +1.71±0.15D, p=0.99). As with all the NL-reared monkeys, the refractive alterations in DL-reared monkeys were axial in nature.
In primates, DL does not appear to produce myopia or to exaggerate either FDM or lens-induced myopia. However, it is possible that DL is a risk factor for myopia because low lighting levels reduce the eye’s response to myopic defocus.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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